The present invention relates generally to semiconductor fabrication and more specifically to methods of forming dual thickness gate oxide layers.
The current process to grow dual thickness gate oxide layers is: forming a first gate oxide on a silicon substrate; masking a portion of the first gate oxide with a photoresist layer; wet etching to remove the exposed portion of the first gate oxide; stripping the photoresist masking layer; then growing gate oxide at the wet etched silicon substrate portion and additional gate oxide at the first gate oxide portion to form dual thickness gate oxide portions of about 70 xc3x85 and about 140 xc3x85.
U.S. Pat. No. 5,918,116 to Chittipeddi describes a dual gate oxide process that forms a thicker oxide using an amorphizing ion implantation using, for example, silicon, fluorine, arsenic and mixtures thereof.
U.S. Pat. No. 6,133,164 to Kim describes a dual oxide process using an oxygen implant.
U.S. Pat. Nos. 5,920,779 to Sun et al., U.S. Pat. No. 6,093,659 to Grider et al., U.S. Pat. No. 6,030,862 to Kepler and U.S. Pat. No. 6,165,849 to An et al. are related dual oxide and ion implantation patents.
Accordingly, it is an object of one or more embodiments of the present invention to provide an improved method of forming dual thickness gate oxide layers.
Other objects will appear hereinafter.
It has now been discovered that the above and other objects of the present invention may be accomplished in the following manner. Specifically, a structure having at least a first area and a second area is provided. The second area of the structure is masked. Ion implanting Si4+or Ge4+ions into the unmasked first area of the structure to form an amorphous layer within the first area of the structure. The second area of the structure is unmasked. The first and second areas of the structure are oxidized to form: a first gate oxide layer upon the structure within the first area; and a second gate oxide layer upon the structure within the second area. The first gate oxide layer having a greater thickness than the second gate oxide layer, completing formation of the dual thickness gate oxide layers.